Electrode joint



Dec. 16, 1930. c. KUHLMANN 1,785,587

ELECTRODE JOINT Filed June 7, 1928 Patented Dec. 16, 1930 UNITED STATES PATENT OFFICE CLEMENS KUHLMANN, OF RATIIBOR, GERMANY, ASSIGNOR TO SIEMENS l-LANIAWERKE AKTIENGESELLSGHAFT FOR KOHLEFAIBRIKATE, OF BERLIN-LIGHTENBERG, GER- MANY, A CORPORATION OF GERMANY ELECTRODE JOINT Application filed June 7, 1928, Serial No. 283,727, and in Germany July 2, 1927.

This invention relates to a method of connecting electrodes by means of which the stump of an old electrode is united with a new electrode for avoiding loss of material. It has already been proposed to unite electrodes in such a manner that the electrodes to be connected are provided at their ends with similar threads for the reception of a separate nipple. For connecting the two electrodes the nipple is screwed into one ofthe threaded holes and the new electrode is screwed on to the projecting half of the nipple. Such nipples have been made either of the same material as the electrodes or, in order to reduce theresistance at the joint, they have been made of more conductive material, such as graphite or metal, or carbon electrodes have had metal cast into them. This method of connection has many drawbacks and for this reason it has ,been proposed to turn ofi' the electrodes at one end and to provide them with a conical thread, which fits in a corresponding thread in the other electrode. In the case of burned electrodes it is very diflicult to cut threads in them owing to their hardness and the wastage in turning tools and diamonds being very heavy.

It has been found that the cutting of 9 threads can be entirely eliminated if the electrodes are provided at one end with a spigot only, which fits accurately into a corresponding hole in the other electrode, and that theelectrodes prepared in this manner are united by applying electrode cement to the spigot and the corresponding hole, the electrodes being thereupon united in a suitable mahner for instance by turning them with respect to one anotheror by pressing them together. The spigot may be made of any sha e, for instance cylindrical or conical, or t e spigot may be four-sided, either conical or straight. Conical spigots'have been found to be particularly suitable for the purpose. It has also been found to be of advantage to provide the electrode at the place where it has a socket corresponding to the shape of the spigot with one or more holes for allowing the air and any superflous cement to escape through the holes. Both the spigot and the socket may readily be made when the electrode is in the green state, i. e. before it has been burned, and any subsequent tooling, when the carbon is in the burned state can be easily carried out without the use of turning tools or diamonds by means of grinding discs. A further advantage of the new method consists in this that with it electrodes of rectangular cross-section can easily be joined without any danger of the joined electrodes canting. In order to prevent the joined electrodes sliding with respect to one another the part forming the joint may be provided'at one or more places with holes,- pins of metal or carbon being inserted in the said holes, which when cemented in prevent the electrodes .coming apart. This securing of the joint is generally necessary as otherwise there is a danger of the joint not being able to withstand the great pull acting on it in the case of heavy electrodes.

It has also been found that the connection between the two electrodes can be secured in a still simpler manner by providing both the spigot and the socket with one or more peripheral grooves into which a refractory cement can be poured. The cement is introduced through one or more lateral holes drilled into the electrode having the socket. For cementing the electrodes together any suitable cement may be used. A paste con sisting of tar and carbon, which hardens at a relatively low heat, has been found to be very suitable. I

.In the accompanying drawing two constructional examples of the electrode connection according to the invention are shown.

In Fig. 1 one electrode a has a conical spigot 12 which fits accurately into the corresponding socket in the other electrode a. The latter is half bored through at the place 03 for allowing the air and the superfluous cement to escape. The electrode joint has a further hole 6 extending through the walls of the socket and through the spigot 12. It serves for the reception of pins of metal or carbon, the said pins extending Inihw' through the entire joint or only beinglnserted from either side until they extend it.-

to the spigot. The holes need only be a few millimetres in diameter and any'number of such holes may be provided. InFig. 2 one electrode a has a spigot 12 at its end which fits accurately into the corresponding socket in 5 the other electrode 0. Around the spigot b a peripheral groove 9 is formed by turning or milling, which corresponds to a similar groove '9 milled in the socket. Into this 10 groove a refractory cement is poured or forced through the hole f, filling the grooves g and g and thereby forming a solid ring which secures the spigot in the socket so that it cannot slip out. The hole d acts as a vent for the air or the superfluous cement when the two electrodes are pressed together.

What I claim is:

For carrying out the .method of uniting the stump of an old electrode to a new electrode in electric furnaces requiring a continuous feed of the electrodes into the furnace to make up for-the electrode material consumed in the furnace, the combination of carbon electrodes having a spigot at one end and a socket at the other end forminga counterpart of said spigot and groovesin the walls of said socket and spigot, with cement interposed between said socket and spigot so as to cover the entire engaging surfaces of the spigot and socket and cement passed into said grooves, as and for the purposes set forth. a

In testimony whereof I have signed my name to this specification. OLELIENS KUHLMANN. 

